In the electronics industry, a continuing objective is to further and further reduce the size of electronic devices while simultaneously increasing performance and speed. To accomplish this, increased miniaturization of integrated circuit (“IC”) packages for these devices is becoming increasingly essential. Cellular telephones, personal data devices, notebook computers, portable music players, camcorders, and digital cameras are but a few of the consumer products that require and benefit from this ongoing miniaturization of sophisticated electronics.
IC assemblies for such complex electronic systems typically have a large number of interconnected IC chips, or dies. The IC dies are usually made from a semiconductor material such as silicon (Si) or gallium arsenide (GaAs). During manufacture, the several semiconductor devices on the IC dies are formed on the dies in various layers using photolithographic techniques.
After manufacture, the IC dies are typically incorporated into IC packages that may contain one or several such dies. Typically, a die is mounted on the surface of a substrate by a layer of epoxy, and electrical contact pads on the upper surface of the die are then connected to the substrate by gold bond wires. In lieu of contact pads used for gold bond wires, solder balls can also be provided on the upper (i.e., active) surface of the die for connections between the die and the substrate; in which case the active surface of the die is face down. A molding compound then encapsulates the die and the bond wires, providing environmental protection and defining the semiconductor IC package. These IC packages, or modules, are then typically mounted on printed circuit boards.
Heat management through such an IC package structure can be critical. The internal thermal resistance and thermal performance of the packaged die are determined by a series of heat flow paths. By making high heat conductivity connections between the bottom of the die and the package substrate, the heat generated by the die can be transferred efficiently from the die to the substrate and then out of the IC package. Often, however, the amount of heat generated in the die is more than can be efficiently transferred in this manner, thus requiring the attachment of a heat spreader to the top of the IC package.
With the ever-decreasing sizes of electronic devices, die-sized IC packages have been developed in which the dimensions of the IC package are almost the same as those of the semiconductor die that is encapsulated inside the IC package. With dimensions so small, it is very difficult to cost-effectively mount die-sized heat spreaders on die-sized IC packages. As a result, some IC packages are mounted on circuit boards without a heat spreader. This may reduce the overall manufacturing and assembly costs, but it increases the risk of making the encapsulated semiconductor die prone to temperature-related damage and lower operating efficiency.
It is similarly difficult and expensive to pre-attach external individual heat spreaders to such small, die-sized IC packages in the factory, or to embed individual heat spreaders into the IC packages themselves as they are being manufactured, where such individual heat spreaders are each made for each package. Mounting a die-sized heat spreader accurately onto an IC package is a process that requires high mounting precision, which adversely increases overall packaging time and costs. Likewise, it is very difficult to control and maintain the precise alignment required to position a heat spreader for embedding within an IC package during encapsulation while the package is being manufactured.
These problems are made even worse by modern, high-performance package configurations. For example, in an effort to improve heat conduction downwardly to the motherboard, high thermal conductivity (“high-k”) epoxy molding compounds (“EMCs”) and multi-layer substrates have been used. However, high-k EMCs are expensive and difficult to process. Moreover, their high filler content increases stresses in the IC packages and on the die surfaces. Multi-layer substrates are also expensive, and they remove heat only through the motherboard. Therefore, external heat spreaders may still be needed, especially for a motherboard that has several heat-generating IC packages thereon.
Thus, a need remains for economical, readily manufacturable heat spreaders for small, die-sized IC packages, and particularly for heat spreaders that can be easily embedded directly within such packages. In view of the ever-increasing need to reduce costs and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.